In a 6-7 week period, male and female ring doves court, incubate eggs, brood young and then begin a new cycle of courtship, incubation and brooding. The aim of the present research is to investigate the relationship between hormonal and behavioral changes seen during the reproductive cycle of the ring dove (Streptopelia risoria). Future research will be oriented in the following major areas: 1. We have shown that in male doves, testosterone and dihydrotestsoterone levels are higher during courtship than in other phases of the breeding cycle. We plan to a) examine male-female pairs and to describe behavioral correlates of changing testosterone levels by doing behavioral observations and taking repeated blood-sample in the same individuals, b) examine whether a change in testosterone level occurs in male-male pairs and whether this relates to dominance status of the individuals involved. 2. I have shown that the male's (but not the female's) crop is already developed (reflecting prolactin secretion) at the beginning of incubation in the second of two uniterrupted breeding cycles. I plan to a) observe incubation behavior in consecutive uniterrupted cycles to determine whether there are behavioral correlates of this sex difference in prolactin secretion. 3. Previous work has shown that males incubate from 10 A.M. to 4 P.M. during the day and females incubate the rest of the time. I plan to a) examine the temporal pattern of incubation in male-male and female-female pairs of doves and to b) measure corticosterone and progresterone at 4-hour intervals in both seexes to determine whether there is a circadian rhythm in the secretion of those steroids, and whether it differes in the sexes. 4. I have shown that dexamethasone (a synthetic analogue of cortisol) blocks prolactin secretion in doves. If corticoids have this effect in mammals, this may prove to be a highly significant finding. I plan to determine whether dexamethasone blocks prolactin secretion in lactating rats by measuring circulating prolactin levels by radioimmunoassay.